488 CONTROLLER
62
PPOLL CONFIG or PPC Command
PPOLL CONFIG (Parallel Poll Configure) configures the Parallel Poll response of a specified bus device.
Not all devices support Parallel Polling and, among those that do, not all support software control of their
Parallel Poll response. Some devices are configured by internal switches.
The Parallel Poll response is set by a four-bit binary number (S P2 P1 P0), response. The most significant bit
of response is the Sense (S) bit. The Sense bit is used to determine when the device will assert its Parallel
Poll response. Each bus device has an internal individual status (
ist
). The Parallel Poll response will be
asserted when this
ist
equals the Sense bit value.
ist
is normally a logical “1” when the device requires
attention, so the S bit should normally also be a logical “1.” If the S bit is “0,” then the device will assert its
Parallel Poll response when its
ist
is a logical “0,” i.e. it does not require attention. However, the meaning of
ist
can vary between devices, so refer to your IEEE bus device documentation.
The remaining 3 least significant bits of response, P2, P1, and P0, specify which DIO bus data line will be
asserted by the device in response to a Parallel Poll. These bits form a binary number with a value from 0
through 7, specifying data lines DIO1 through DIO8, respectively.
SYNTAX
PPOLL CONFIG addr;response
or
PPOLL C addr;response
or
PPC addr;response
addr
is a bus address.
response
is the decimal equivalent of the four binary bits S, P2, P1, and P0.
RESPONSE
None
MODE
CA
BUS STATES
ATNUNL, MTA, LAG, PPC, PPE
EXAMPLES:
PRINT #1,"PPC23;&H0D"
Configure device 23 to assert DIO6 when it desires service and it is Parallel Polled (&H0D = 1101 binary;
S = 1, P2P1P0 = 101 = 5 decimal = DIO6).
PPOLL DISABLE or PPD Command
PPOLL DISABLE disables the Parallel Poll response of selected bus devices.
SYNTAX
PPOLL DISABLE addr[,addr]
or
PPOLL D addr[,addr]
or
PPD addr[,addr]
addr
is a bus device address
RESPONSE
None
MODE
CA
BUS STATES
ATNUNL, MTA, LAG, PPC, PPD
